Helium purifier

ABSTRACT

A continuous production and delivery of ultrapure helium involving dual adsorption columns is characterized by a helium purifying operation in one of the columns concurrently with preparation for such operation in the other column by regeneration and pressurization of the adsorbent. A pair of the helium product is utilized upon delivery from one column to purge impurities from the other column and pressurize its adsorbent. Continuous cycling of the sequence of helium purification alternating with an application of heat, together with a restricted flow of purging helium for column regeneration and pressurization, is coordinate for the respective columns by operation of a time regulated program control.

United States Patent Seitz et al.

[ HELIUM PURIFIER [72] Inventors: Charles A. Seitz; Winston M.

Bodine, both of Amarillo, Tex.

' [73] V Assignee: The United States of America as represented by theSecretary of the Interior [22] Filed: Sept. 8, 1970 [21] Appl. No.:70,136

52 us. Cl. ..55/62, 55/66, 55/208,

62/ l 8, 62/40 [51] Int. Cl. ..B0ld 53/04, F252 3/00 [58] Field ofSearch ..55/62, 66, 74, 179, 208, 387, 55/162; 62/18, 40

[15] 3,683,589 [451 Aug. .15, 1972 3,243,938 4/1966 Lavery et al ..55/62Primary Examiner-Charles N. Hart Attorney-Emest S. Cohen and GerstenSadowsky s71 ABSTRACT A continuous production and delivery of ultrapurehelium involving dual adsorption columns is characterized by a heliumpurifying operation in one of the columns concurrently with preparationfor such operation in the other column by regeneration andpressurization of the adsorbent. A pair of the helium product isutilized upon delivery from one column to purge impurities from theother column and pressurize its adsorbent. Continuous cycling of thesequence of helium purification alternating with an application of heat,together with a restricted flow of purging helium for columnregeneration and pressurization, is coordinate for the respectivecolumns by operation of a time regulated program control.

10 Claims, 4 Drawing Figures PATENTEDAU: 15 we saw 1 0F 3 INVENTORS F/CHARLES A. 55/72 W/A/STO/V M. BUD/NE P'A'TE'N'TEDAus 15 m2 SHEET 3 [IF 3TIME OF cY LE HOURS F/G 3 H *3 *5 *1 9 N 1 m .1 VALVE 30s OPENED 12HOURS CLOSED l2 HOURS COL VALVE 3|0 CLOSED IZHRS-SMINS RZZ EQ CLOSEDlOHRS-ISMINS VALVE 304 oPENED IZHRS- M|NS P oPENED arms-45mm HEATER soOFF|2 rms-smms 92 M OFF lOHRS-ZSMINS VALVE 408 CLOSED l2 HOURS OPENED l2HOURS COL v 4|o ghqfl i $591 (OWNS CLOSED 22 HRS ISMINS V 404 gfifimgl ZP IOMINS OPENED 2| HRS M|NS HTR. I60 gK 'T ffi Mms OFF 22 HRS 2s NuNsINVENTORS CHARL ES A. /77

WINSTON M. BOD/IVE HELIUM PURIFIER The invention relates to a method andapparatus for producing ultrapurified helium having its impuritiesreduced to a less than 1 part per billion (ppb). Helium of standardquality, or Grade A helium, having about parts per million (ppm) totalimpurities must be improved for certain scientific uses such as acoolant medium in nuclear reactors, an inert blanketing gas for crystalgrowing, and a carrier gas for helium ionization chromatographicanalyzers. Combinations or trains of known helium purificationprocedures which remove individual impurities, such as oxygen byreaction with alkali metals, nitrogen by reaction with heated titanium,zirconium or uranium, and hydrogen by diffusion through palladium oroxidation with catalysts, are not practical for a continuing productionof purified helium. A known scheme of helium purification in which allimpurities are removed at one time is dependent on the permeation ofhelium through quartz at a higher rate than all the other impurities.However, this scheme does not necessarily produce ultrapure helium sincethe resultant mixture contains hydrogen and neon which are known to passthrough quartz in significant amounts. These attempts, and others toenhance the purity of helium, such as using organic membranes in series,have not satisfactorily produced an ultrapure helium, and entail highcosts of heating, or recompression, or both.

High purity helium can be obtained by the regasification of filteredhelium taken from beneath the surface of liquid helium. However,purification of helium by first cooling it to 42 K is an expensivemethod for ap plication to continuous production. Known methods ofpurifying helium utilizing highly activated adsorbents at lowtemperatures, as presently practiced on a commercial scale, do notfurnish an ultrapure helium since the impurity neon is allowed to passthrough the appertaining adsorbent beds virtually unchanged inconcentration. Purification of helium by adsorption can be made moreefficient by reducing the adsorbent temperature from 77 K of liquidnitrogen, by means of a helium refrigerator, to a lower temperaturewhereat neon and all other impurities are reduced below detectablelimits. However, the cost of helium refrigeration is relatively high andequipment for carrying out this type of purification is relativelyscarce. Distinguishing the present invention from the methods heretoforenoted is the use therein of an adsorbent material at the temperature ofliquid nitrogen to make possible a continuous operation producingultrapure helium. Moreover, the invention can be safely kept inproduction for extended periods of time with only periodic observationsby an operator, and remains reasonably efficient in the utilization ofboth helium and cryogen.

Apparatus according to the invention operates automatically to deliver acontinuous stream of purified helium. This operation importantlyinvolves a two part purification instrumentality of the apparatus havingin each of its parts an adsorbent material generally filling anenclosure positioned under an inverted container forming an insulatorshroud. Gas periodically trapped under this shroud constituting it asuperior heat shield makes possible dual temperature operations whichlie at the heart of the invention. Both parts are adapted to functiontogether suspended within liquid nitrogen, each operating in turnout-of-phase as a low temperature helium purifier and as a relativelyhigh temperature regenerator of the absorbent material containedtherein. More specifically, the respective shrouds communicate throughseparate valved conduit systems which at appropriately timed intervalsin an operational sequence of the invention cause liquid nitrogen to beforced out from within the confines of one shroud, and away from theenclosure thereunder, and replaced by nitrogen gas which allows a highertemperature for regeneration of the enclosed adsorbent material.Further, since a purification operation in one part of the apparatus.continues while regeneration of adsorbent material occurs in the otherpart, purified helium in the apparatus is available as a requisite gasfor purging in carrying forward the regeneration of the other partenclosure, as well as repressun'ng this enclosure when it issubsequently recooled. Continuous cyclic operation of the apparatuswhich enables uninterrupted productive operation is predetermined by thesetting of a program control mechanism employing timer driven camactuators for switches in energizing circuits to valve actuatingsolenoids and heaters cooperatively associated with the respectiveenclosures.

A principal object of present invention is therefore to provide apractical method of producing ultrapure heliurn which is both economicaland reliable.

A further object of the invention is to provide a simplified apparatusuniquely adapted to'produce an ultrapure gas.

A still further object of the invention is to provide an automaticallycontrolled apparatus which is continuously operable for producing asteady supply of ultrapure helium.

These and other objects and advantages of the invention will become morefully apparent from the following detailed description of the inventionset forth herein and from the accompanying drawing madea part hereof, inwhich:

FIG. 1 is a sectional view, which'is partly schematic, showing theoverall arrangement constituting a purification apparatus according tothe present invention;

FIG. 2 is a schematic diagram of electrical circuitry .and associateddevices which constitute the program controller of the invention;

FIG. 3 is a time cycle chart illusu'afing a program of operationalsequences assigned to components of the invention controllingfundamental functions thereof; and

FIG. 4 is a cross-sectional and in part schematic representation of aportion of the apparatus shown as having in association therewith arefrigerant level sensor and circuitry responding thereto forcontrolling a refrigerant filling mechanism.

Dual purifier columns 10 and 12 employed in a preferred apparatusaccording to the invention, as shown in FIG. I, are arranged foroperation in a drumlike tank assembly 16. An evacuated double wall,stainless steel construction used in fabricating a container part 18 oftank assembly 16, obtains therefor the insulation properties of a dewarvessel. Container 18 is recessed at its bottom so as to create a doublethickness peripheral portion providing a support edge for a base 20 ofthe apparatus. A flat upper peripheral edge of container 18 has weldedthereto a flat flanged collar 22 wherein a tank cover plate 24 isadapted to be positioned by alignment of its edge with that of thecollar and secured tightly by flange bolts or clips. Cover 24 ischaracterized by a pair of access holes 26 and 28 having a symmetricaldisposition on the cover which situates each hole centrally over arespective one-half of the space within container 18. Flanged teefittings 30 and 32 are positioned to cover holes 26 and 28,respectively, such that their flanges are conveniently securable to theupper surface of cover plate 24. Internally threaded openings infittings 30 and 32 have secured therein further fittings from whichpurifier columns and 12, respectively, and their appurtenances, dependso as to be maintained within separate halves of container l8out-of-contact with the container and each other.

The aforementioned purifier columns are essentially tubular structureswhich, when filled with an adsorbing material, will cause eitherpermanent or temporary retention of the impurities in a gas fedtherethrough so as to cause a temporary decrease or elimination of theseimpurities from the gas as discharged from the purifier. Since therespective purifier columns of the present invention together with thevalving arrangements therefor are in essence structurally andfunctionally identical, a detailed description thereof is, in general,given with reference to purifier column 10. An adsorbent agent,comprising activated coconut charcoal 40, is confined within acapsule-like canister 42, which can be conveniently made of stainlesssteel. An extended, thin-walled tubular casing 44 axially disposedwithin canister 42, constituting a thermowell therein, is open at thebottom end thereof. The cylindrical elongation 46 of canister 42 mergesat the extremities thereof with hemispherical end sections 48 and 50which have internally threaded holes through central thickened partsthereof. Fastened in the holes of sections 48 and 50 are flanged,threaded closure caps 52 and 54, respectively. Closure cap 54 is axiallytraversed by a passage 56 having secured to the inner opening thereofthe rim of the open end of tubular casing 44. Cap 54 thus maintainscasing 44 concentrically oriented with respect to canister 42, anddisposes the closed end of the casing spaced a short distance from theinner opening of a passage 58 centrally traversing closure cap 52. Aswas hereinbefore indicated, casing 44 houses a heater unit 60 wherein aresistance wire 62 is extended from connections to electrical leads 64which traverse cap passage 56 and extend out of the apparatus, throughappropriate fittings in cover 24, to a heat controller device 540appearing in FIG. 2.

Canister 42 is held centrally positioned under an enveloping insulatorstructure comprising a shroud 70. Double wall stainless steel shellsforming shroud 70 seal in evacuated space so as to provide an insulatingpartition which appears in FIG. 1 as a domed cylinder having an openbottom. Above an axial necked-in section 74 of shroud 70 rises avertical conduit 76 thereof which is engaged to a lower opening of teefitting 30 by a fluid tight coupling 78 screwed into the fitting openingand onto a threaded end of conduit 76. In an upper opening of fitting 30is secured a reducer tee fitting 82 from which canister 42 is suspendedby its connection to a conduit 84 attached to the fitting. Theseconnections are effected by securing an upper rim portion of conduit 84in a lower opening of fitting 82, and a lower rim portion of the conduitin the outer opening of closure cap passage 58. By thus suspendingcanister 42 within shroud there is enclosed an annular space 86 whichprovides an appreciable separation between these parts. Moreover,conduit 84 is thereby located concentrically within conduit 76 to definean annular space 88 therebetween. Also placed in concentric relationshipwith conduit 84 is an upper extension of a further conduit 90 whichextends through conduit 84 to define a still further annular space 92therebetween. A lower extension of conduit 90 passes down into canister42, and traverses charcoal 40 so as to place an open end 94 thereof inthe charcoal adjacent the bottom of the canister. As is now evident withfurther reference to Flg. 1, conduit 90 provides by its upper and lowerextensions, and an inclined bridging part thereof situated above casing44, a continuous passage for flow from above a coupling cap 96 infitting 82 to opening 94 of the conduit. A further coupling cap 98 isprovided to secure an exterior conduit 100 to a further opening infitting 82 and thereby facilitate fluid communication between conduit100 and the interior of canister 42 by way of the flow passage infitting 82 and annular space 92 in conduit 84. Similarly a coupling cap102 secures an exterior conduit 104 to fitting 30, and facilitates afluid communication between conduit 104 and annular space 86 in shroud70 by way of the flow passage in fitting 30 and annular space 88 inconduit 76.

As was previously indicated, parts identified with respect to purifiercolumn 10 find their counterparts in purifier column 12. In brief,column 12 includes an ad sorbent agent of activated coconut charcoalconfined in a canister 142 comprised by an extended cylindrical shell146 which at its opposite ends becomes hemispherical in parts 148 and150, respectively. Closure caps 152 and 154, secured in axially alignedend openings of the canister, have axial passages 158 and 156 thereinwhich open within the canister at the upper and lower ends thereof,respectively. A tubular casing 144 axially disposed within the canistercontains a heater unit 160 wherein an extended resistance wire 162 hasconnections 164 to a remote controller 554, appearing in FIG. 2. Teefitting 32 has secured thereto a reducer tee fitting 182 which in turnhas secured in a lower opening thereof a vertically disposed conduit184. Canister 142 is vertically positioned in container 18, level withcanister 42, by suspension from conduit 184 attached within a closurecap passage 158 of canister 142. A vacuum jacketed insulating shroud170, open at its bottom, comprises an upper conduit part 176 which byits attachment in a lower opening of fitting 32 suspends the shroud toenvelop canister 142. Provisions to channel gas which has been purified,in a manner to be hereinafter more fully explained, from a lower partinside canister 142 to outside column 12, includes a further conduitwhich rises through canister 142 from its opening 194 in the aforesaidlower part and extends axially within conduit 184 to emerge above acoupling cap 196 secured in a upper opening of fitting 182. A fluidchannel communicating an upper part inside of canister 142 with anexterior conduit 200 coupled in a further opening of fitting 182, isprovided in column 12 by way of an annular space 192, defined betweenconduits 184 and 190, which opens into the fluid passage in fitting 182leading to conduit 200. A fluid channel communicating an annular space186 between shroud 170 and canister 142 with an exterior conduit 204,coupled to a further opening in fitting 32, is provided in column 12through an annular space 188 defined between conduits 176 and 1, whichopens into the fluid passage in fitting 32 leading to conduit 204.Accordingly, when properly situated in tank 16, the respective columnarstructures, including the shrouds thereof, are spaced away from allsurfaces within container 18, and each other, such that requisitesurfaces thereof are contacted by liquid nitrogen 250 filling thecontainer to a level reaching slightly above the lower ends of shroudconduits 76 and 176.

Provisions made for supplying liquid nitrogen as required to maintain aproper level in container 18 include a level controller arrangement ofthe type illustrated in FIG. 4. Nitrogen lost in the procedure to behereinafter more fully explained, is replenished from an outside sourceby way of a line 600 in which flow is regulated by a control valve 602.A solenoid 604 is adapted to actuate the valve to open when energized ina power circuit 606 which is completed by closure of a pressure actuatedswitch 608. Contacts 610 of the switch are operated by pressure changein a bellows unit made up of a stainless steel capillary tubing 612opening at its top end into a bulb 614. This unit is completely filledthrough a lower end opening of tubing 612 with methane at atmosphericpressure whereupon the end is crimped, cut, and silver brazed-to form aleak proof joint constituting a sensing end 616 for the unit.

A relatively thick copper wire 618 is soldered to sensing end 616 andwrapped around the capillary so as to extend upward. A suitable couplingcollar set into container cover 24 maintains tubing 612 verticallydisposed in the cover with sensing end 616 in contact with liquidnitrogen 250. Since wire 618 is thus situated to reach into the warmergaseous region of container 18, it forms a thermal conductor to warmsensing end 616 when the liquid nitrogen level drops below this end. Thetop of bulb 614 is mechanically linked to the switch arm of contacts 610so as to drive the arm to close the contacts when the bulb expands. Theswitch is adjusted by inserting sensing end 616 into liquid nitrogen andturning an adjustment screw (not shown) of the bellows structure untilthe switch contacts open. Since the enclosed methane is a solid at thetemperature of liquid nitrogen and changes pressure rapidly withtemperature rise above this point, a drop of the liquid nitrogen surfaceto even a few millimeters below sensing end 616 causes sufficientexpansion of bulb 614 to effect completion of energizing circuit 606 atcontacts 610. This arrangement is made particularly sensitive by theaction of heat sink 618. The resultant opening of valve 602 and theconsequent release of liquid nitrogen to supply container 18, raises thelevel therein to where liquid nitrogen covers sensing end 616.Responsive to the resultant pressure drop in the bellows structureswitch contacts 610 reopen in circuit 606, and valve 602 closes. Foaminsulation 620 under cover and similar insulation 622 adjacent pipe 600,function in a conventional manner to improve the efficiency of theliquid level controller. A pilot light 624 in circuit 606, operates inthe usual way to indicate periods during which liquid nitrogen issupplied to the apparatus.

Apparatus according to the invention further employs in connection withcanisters 42 and 142, a valving system for controlling the flow ofhelium feed input and venting, and a product or purified helium output,and in connection with shrouds and 170, a valving system for filling andventing nitrogen from under the shrouds. Valves also provided includerelief valves in the feed input and venting conduits, check and meteringvalves in product helium conduits, and an adjustable needle valve in aconduit connecting the canisters for facilitating a back flow procedure,to be hereinafter more fully explained. Referring now to FIG. 1,takentogether with FIG. 2, the aforesaid valving systems will be seen ascomprising separate sets of electrically controlled solenoid actuatedvalves 300 and 302 which selectively function to coordinate theoperations in columnar structures 10 and 12, respectively. A lowpressure, solenoid actuated, normally open valve 304, associated withcolumn 10, determines the flow of nitrogen gas from under shroud 70 andthrough annular space 86, by controlling gas flow from conduit 104 to anitrogen vent conduit 106. Helium flow to and from the confines ofcylinder 42 is effectively channeled through conduit by way of a reliefvalve 306 wherefrom helium passes into branching conduits 108 and 110having operable therein solenoid actuated, normally closed valves 308and 310, respectively. Relief valve 306 is preceded in the linetheretoby a pressure gage 112 in a take-off conduit connected to conduit100. Accordingly, valve 308 is operable to allow flow of a helium feedgas from an input conduit 114, which by way of conduit 108, 110 and 100,enters canister 42, and valve 310 is operable to allow out-flow of ahelium gas discharged from canister 42, which by way of conduits 100 and110, vents through conduit 116. Product helium in conduit 90 flowstherefrom by way of a oneway check valve 312 opening into a conduit 118, and exits in a product output conduit under control of a manuallyoperable valve 314.

Solenoid actuated valves 404, 408 and 410 of valve set 302, correspondin form and function to valves comprising set 300. Normally open valve404 provides a passage wherefrom nitrogen gas arising from under shroud170, and passing through its annular space 186, further annular space188, and conduit 204, is vented through conduit 206. Actuation ofnormally closed valve 408 completes a passage wherein helium feed gassupplied from an input feed conduit 214 flows to canister 142 by way ofconduits 208, 210, and 200, and annular space 192. Actuation of normallyclosed valve 410 completes a passage wherein contaminated helium gasarising from inside canister 142 flows out through annular space 192,and conduits 200 and 210, wherefrom the gas is vented through a conduit216. Gas flow between conduit 200 and conduits 208 and 210 passesthrough a relief valve 1 and is monitored by a pressure gage 212. Heliumpurified by operation of the invention exits canister 142 in conduit190, wherefrom this helium passes through a check valve 412, a conduit218 and a manually controlled valve 414, and is supplied to storage or apoint of utilization in conduit 220. A directional reversal of gas flowthrough conduits 90 and 190, which occurs every half cycle in theregular operation of the apparatus, to be hereinafter more fullyexplained, is facilitated by intercolumnar connection conduits 422 and424 containing needle valve 420A conventional needle valve havingutility in the preferred embodiment of the invention operates up to aline pressure of 3,000 psi, while allowing the same flow in eachdirection or at least within ten percent of the set How in onedirection. A further conduit connection 430 between output conduits 118and 218 allows delivery of purified helium from the respective canistersthrough either one or both of the control valves 314 and 414, by way ofthe respective product output conduits 120 and 220, connected thereto.

Operations in valve sets 300 and 302, and activations of heater devices60 and 160, occur in response to the action of a cam controlledmicro-switch arrangement 500, schematically represented in FIG. 2. Cams501 to 508, inclusive, of this arrangement are positioned on a shaft ofa linkage 509 which is driven by its connection to a controller-timermotor 510. Preset, single poledouble throw switches 511 to 518,inclusive, have switch arms disposed for displacement between fixedcontacts of these switches by cams 501 to 508, respectively, in aconventional manner. Switches 511, S12, and 517 appear preset such thatthey initially complete circuits wherein the solenoids of valves 304,310, and 408 are energized. However, solenoid actuation in valve 304,effects closure thereof whereas solenoids in valves 310 and 408 areactuated to attain the open condition of these valves. Further, at thestart of the cyclic operation of the invention, to be hereinafter morefully explained, cam 504 is disposed to effect completion of a circuitwherein resistance wire 62 of heater 60 is energized. Energizing voltagefor arrangement 500 is derived from an a-c source 520, and suppliedbetween leads 522 and 523. Thus, energization of timer motor 510 is in acircuit traceable between the aforesaid supply leads on leads 525, 526,through an on-off switch 528, and leads 529 to 532, inclusive. Aseparate one of a set of manually operable, single pole-double throwswitches 541 to 548, inclusive, is included in each of the camcontrolled circuits of the valve solenoids and heaters. Thus, theaforesaid cam control can be over-ridden in any of the circuits byoperating the related one of override switches 541 to 548 to open at onecontact thereof the connection to the micro-switch arm, and complete atthe other contact thereof a circuit directly leading to the voltagesource.

Energization of the valve solenoids is accomplished in circuitstraceable from voltage source 520. on leads 522, 525, 534, a cam switchbus lead 536, through micro-switches having connections to lead 536, theoverride switches, and on leads extending to the valves and backtherefrom on a common return lead 538 to supply lead 523. Heaters 60 and160 are energized by power applied in circuits similarly traceable withthe exception that powerstats 540 and 554 are included by connections inparallel on leads 556, 558, 560, and 562, 564, across voltage supplyleads 522 and 523. Micro-switches 514 and 518 for controlling the heaterenergizing circuits are in turn respectively connected to power take-offcontact arms 550 and 552 of the respective power-stats instead ofdirectly to source 520. Pilot lights such as lamp 565, and suitablevoltage modifying resistances such as resistors 566 connected in seriestherewith by leads 5 67, are connected by way of a common lead 568across the respective circuits of the several powered parts of thecircuitry so as to provide indications of the activity of such parts.

Start-up for cyclic operation, and the subsequent repeated operationalcyclings according to the invention are now explained with reference tothe drawing including FIG. 3 showing a timing chart for a regular cycleof operation. Operational control cams 501 to 508 are originally fixedto shaft 509 at the positions indicated in FIG. 2, where the camsdetermine the setting of micro-switches 511 to 518, correspondingthereto, such that contact arms of micro-switches 517, 512, 511, and 514are each in place for completing a circuit from power source bus lead536 to valve actuators. The resulting solenoid actuations set valves 408and 310 open, and valve 304 closed, while the concomitant energizationof resistance wire 62 turns on heater 60. Valve 308 remains closed sinceits solenoid circuit is interrupted at micro-switch 513. Solenoidcircuits are also interrupted at micro-switches 515, 516, and 518 withthe result that normally open valve 404 stands open whereas valve 410 isclosed and heater 160 is in its ofi' condition. Container 18 is suppliedwith liquid nitrogen 250 to a level therein which just covers theshrouds at their necked-in portions, as appears in FIG. 1. Powerstat arm550 is adjusted to raise the temperature in canister 42 to above 150 C.The heat thus achieved is maintained for about 5 hours during which timecanister 42 is purged with helium being drawn through the system,including canister 142 and valve 420, at about 200 to 300 cm per minute.Temperatures in the respective columns are monitored separately bythermocouples appropriately affixed in contact with the outer walls ofthe respective canisters, and having electrical connections extending toremote meters (not shown). Heat added to column 10, as described, causesgaseous nitrogen to form, and since closed valve 304 blocks venting ofthe gas, liquid nitrogen is forced from annular spaces 86 and 88 and outof the open bottom of shroud 70. The resulting in sulating shieldbetween canister 42 and liquid nitrogen outside of shroud allows column10 to be heated to a temperature much above that of liquid nitrogen. Itwill also be recognized that upon heater 60 going to off when vent valve304 opens, liquid nitrogen is allowed to rise inside the aforesaidannular spaces around shroud 70 such that canister 42 is again submergedin liquid nitrogen. This level rises to a height which is maintained incontainer 18 proper.

Helium for purging column 10, including canister 42, first enters atconduit 214 leading to open valve 408, and flows from there throughconduits 208, 200 annular space 192, adsorbent 140, opening 194,conduits 190, 422, valve 420, conduits 424, and 90, opening 94,adsorbent 40, annular space 92, conduits 100, 110, and open valve 310,before exhausting out conduit 116. A purging with helium during a periodof heating, as previously explained, in this instance particularlyeffects the removal of moisture and air from adsorbent 40 resulting fromits exposure to air prior to the packing thereof in canister 42. Thispurging phase in column 10 is brought to completion when cams 501, 502,and 504 are driven to where energizing circuits through the relatedmicro-switches 511, 512, and 514 are interrupted so as to allow theopening of valve 304, the closing of valve 310, and effect thedeenergization turning off heater 60.

The program control is thereafter caused to advance its cams to wherethe micro-switch contacts displaced complete energizing circuits tosupply 520 by way of micro-switches 513, 516, 515, and 518. Resultantsolenoid actuations open valves 308 and 410, and close valve 404, at thesame time heater 160 is turned on in column 12. Closure of valve 404when heater 160 is energized gives rise to an accumulation under shroud170 of gaseous nitrogen which forces liquid nitrogen from under theshroud. The insulation about canister 142 thus produced enables abuild-up of temperature therein exceeding 150C, which is best suited toproper purging of column 12 and reactivation of its adsorbent 140. Apurging condition is maintained for about hours with 200 to 300 cm perminute back flow of helium being supplied by way of open valve 308,passage through canister 42, and valve 420, in the conduits bridging thecolumns. Specifically, helium at valve 308 enters canister 42 fromannular space 92, flows back through adsorbent 40 in this canisterwhereby purified helium passes by way of opening 94 and its conduit 90,conduits 424, 422, and valve 420 therein, conduit 190, out throughopening 194, and through adsorbent 140, annular space 192, conduits 200,and 210, and exits through open valve 410. Thermocouples in contact withcanister 142 permit temperatures therein to be monitored, as washereinbefore explained in connection with canister 42. Once conditionedby the previously explained purging routine, the apparatus according tothe invention is prepared for regular cyclic operations by an adjustmentof needle valve 420 which limits backflow in either directiontherethrough to approximately 100 cm per minute. The lessened backflowis suitable for the continuous cyclic operations of the apparatus now tobe disclosed.

Regular operation of the disclosed embodiment is based on a 24 hourcycle wherein the invention achieves a continuous generation of heliumwith no detectable impurity. In each complete cycle both adsorptioncolumns are used in purifying helium, one column after the other, andboth columns are regenerated for further use, one column after theother. Accordingly, in every half cycle period one column operates topurify helium while the other is in a regeneration or regenerated mode,whereas in the following half cycle period these operational modes arereversed for the respective columns. Thus, following upon completion ofa purifying operation in column 10, the regeneration mode is initiatedtherein. However, production of purifled helium is stopped and theadsorbent is regenerated well in advance of the appearance of the firstcontaminant (neon) to break through the column. Break through times forneon can be determined in advance by continuous analysis of the heliumemerging from the purifier. Only 80 percent or less of this neonbreakthrough time is utilized to assure that neon is not allowed toelute from the column.

Reference to the functional indicators vertically below time designatorst and r. in the 24 hour cycle timing chart of FIG. 3, make evident aregeneration start-up in column 10 requiring closure of gas passagesthrough valves 308, 304, and 410, and open passages for gas throughvalves 310, 408, and 404. In addition, heater 60 must turn on, whereasheater stands off. The control exercised by the timed drive from motor510 upon cams 501 to 508 is accordingly effective to program these camsfor accomplishing the valve and heater conditions necessary forregeneration in column 10. This operative status is illustrated in FIG.2 where cams are shown disposed to effect application of voltage supply520 for energization of valve solenoids and a heater wire, by way of therespective micro-switches 511, 512, 514, and 517, and disconnect thevoltage supply from solenoids and a heater wire at microswitches 513,515, 516 and 518. An approximately 5 minute delay in opening helium ventvalve 310 after the closing of the helium input through valve 308,indicated by the distance from t 6 to t, in FIG. 3, is achieved in theusual manner by a relative disposition between the working surfaces oncams 502 and 503. This delay serves to insure that vent valve 310 is notopened before the closing of the helium feed valve 308 so as to preventunnecessary losses of helium. Upon the start of regeneration in column10, purification of helium is initiated in column 12 as the opening ofvalve 408, at time t shown in FIG. 3, permits a supply of helium fromconduit 214 to enter canister 142 by way of conduits 208 and 200, andannular space 192. Purification of the helium supplied proceedsforthwith since following an earlier regeneration of column 12 more thanadequate time is provided in which temperature and pressure in canister142 are brought to operating conditions, as will be hereinafter morefully explained.

This appears from FIG. 3 which indicates that for the respectiveextended periods from times t and t up to time t helium vent valve 410stands closed to facilitate repressurization, and nitrogen vent valve404 stands open to permit the retention of liquid nitrogen under shroud170 which submerges and recools canister 142 during pressure build-uptherein. However, before regular production cycles in which 1 ppb heliumis delivered a number of automatic cycles are first perrnitted to occur.The extent of pre-production cycling is dependent on the operating linepressure as well as the contaminant content of the gas being processed.In exemplary applications of the invention to purify helium gas havingabout 15 parts per million of neon, operating line pressures of psi and500 psi required two and one-half, and three preparatory cycles,respectively.

A production run sequence of the present invention which follows theoperational start-up and initiation of regeneration of column 10together with helium purification in column 12, is hereinafter disclosedwith particular' reference to the timing chart of FIG. 3. In thissequence regeneration of column 10 commences when heater 60 becomeseffective during the period starting at time t,, and the needle valve420 allows a reverse flow of purified helium drawn from column 12 tosurge through column 10 as the latter is depressurized upon the openingof helium vent valve 310. The temperature produced by heater 60generally does not exceed 0 C in normal operation. Although the use ofas little heat as possible during regeneration is more efficient, atemperature as high as 150 C may occasionally be applied when requiredby gas flow conditions. Requisite backflow through needle valve 420 doesnot normally exceed I cm per minute, and therefore diverts only a smallpart of the purified gas product from column 12. Again referringto FIG.1, this backflow during regeneration of column is traceable from thesupply thereof at helium inlet valve 408, through conduits 208, 200,annular space 192, the substance of adsorbent 140, conduit 190 by way ofits opening 194, conduit 422, valve 420, conduits 424, 90 and itsopening 94, the substance of adsorbent 40, annular space 92, andconduits 100 and 110 to helium vent valve 310, then open.

Regeneration of column 10 reaches completion at time t shown in FIG. 3,when micro-switch 514 responds to displacement of cam 504, andinterrupts the energizing circuit to heater 60. At time t valve 304 ispermitted to open as the action of cam 501 on micro-switch 511 effectsthe interruption of the valve solenoid energizing circuit. Venting ofnitrogen gas through valve 304 allows liquid nitrogen to fill the voidunder shroud 70 and canister 42 is once more submerged in liquidnitrogen. Somewhat earlier, at time t,, helium vent 310 closes uponinterruption of its solenoid energizing circuit at micro-switch 512,with the result that pressure quickly builds-up to about 25 psig due tothe backflow of purified gas from column 12. In the remainder of thehalf cycle ending at the time t column 10 is colled by liquid nitrogenwhich entered the bottom of shroud 70 as rapidly as vaporized nitrogenvented through valve 304. Adsorbent 40 is simultaneously repressurizedwith the purified helium flowing through needle valve 420, and anoperating pressure near 150 psig is reached before column 10 is neededfor the purification operation of the subsequent half of the cycle.Ultrapure helium produced in column 12 during the previously describedregeneration of column 10, less the small amount used in theregeneration, exits the apparatus in conduit 190, passing through checkvalve 412 prior to being removed to instrumentation or storage by way ofconduit 218, flow control valve 414, and conduit 220. Flow from conduit218 into conduit 430 also supplies ultrapure helium to conduit 118wherein control valve 314 is operable to permit delivery of the heliumto output conduit 120 alone, or together with output in conduit 220.

Program control 500, now at time t, of the cycle illustrated in FIG. 3,functions to effect closure of column 12 helium feed valve 408 whileopening helium feed valve 308 of column 10. Shortly thereafter, at timet the program control acts further to close nitrogen vent valve 404 andopen helium vent valve 410 at the same time heater 160 is turned on incolumn 12. Valves 304 and 310, previously set open and closed,respectively, remain unchanged. Column 10 now fully conditioned toproduce ultrapure helium, commences to do so when helium flows throughopen valve 308 and is supplied to canister 42. On the other hand,canister 142, now further insulated by nitrogen gas in annular space186, trapped by closed vent valve 404, undergoes heating by heater 160in its thermowell 144. Reactivation of adsorbent 140 thus proceeds ashelium produced in column 10 is bled from conduit 90 by way of valve420, and channeled through canister 142 to carry gases driven out ofadsorbent 142 through annular space 192 and out of the apparatus by wayof valve 410 and conduit 216. Ultrapure helium product received throughcheck valve 312, is delivered in conduit 118, and through flow controlvalve 314, to conduit 120, and concurrently or alternatively in conduits430 and 218, and flow control valve 414, and conduit 220. Conduitconnection 430 allows pressure in the ultrapure helium beingcontinuously delivered by the apparatus to be equalized as well as itsdelivery from control valves 314 or 414 or both, at the operatorsdiscretion. However, at all times, even when valve operation changes thefeed gas input from one source to another, purified gas is in a regionnever open to air. After the respective appropriate predetermined timest;,, t, and t following the start of regeneration in column 12, heaterstands turned off, nitrogen vent valve 404 stands open to initiaterecooling of canister 142, and valve 410 has closed to allowrepressurizing of the column. Subsequently, the cycle continuesfollowing the regeneration and helium producing sequence of stepsheretofore described in connection with column 10, and concludes at timet when conditions in the columns start to reverse, as hereinbeforedisclosed, for another cyclic operation.

In a further embodiment of the invention a control for intercolumnarvalve 420 is programmed to enable a variable flow through that valve inaccordance with the part of the regeneration cycle in effect. Thus, thecontrol allows a suitably low flow to a canister during the heat purgeportion of the cycle occurring therein, and an increase in flow to acanister following closure of its helium vent or discharge valve so asto allow a more rapid build up pressure in an activated canister. Tothis end valve 420 can be motorized so as to have requisite openings atpreset times, or a second valve, automatically controlled by programmingdevices, can be connected in parallel with valve 420 and opened aboutthe same time as the helium vent valves are closed. Somewhat better useof the purified helium for back purging is made possible under theseconditions since the back flow through valve 420 has to be high enoughto accomplish the repressuring of the activated column to near theoperating line pressure before its next use. However, the repressuringflow is higher than needed for the back purge required for purging theimpurities from the system, and although this is more of a problem athigher pressures it is not a detrimental factor in a practicaloperation.

The amount of highly purified helium produced is dependent upon thepressure at which helium is fed through the apparatus, as well as thechosen cycle time. Operating pressures as high as 1,750 psig can be usedin the disclosed embodiment of the invention. Operation of thisapparatus using a cycle time of 24 hours provided a continuous deliveryof cm per minute of ultrapure helium. When using a cycle time of 12hours, other operating conditions remaining the same, a delivery ofhelium at 400 cm per minute can be achieved.

While a preferred form of the method and apparatus of the invention havebeen described and illustrated, it is to be understood that theinvention is not limited thereby but is susceptible to changes in formand details.

What is claimed is:

1. Method for purifying helium by adsorption of the impurities thereincomprising the steps of maintaining during a first interval of timefirst and second quantities of adsorbing agent at aneffectively constantrelatively low temperature and temperatures ranging from a relativelyhigh temperature to said relatively 'low temperature, respectively, andduring an immediately following second interval of time maintaining saidfirst and second quantities of said adsorbing agent at temperaturesranging from said relatively high temperature to said relatively lowtemperature, and at said relative low temperature, respectively,supplying in each of said succeeding intervals of time a stream of feedhelium for flowing contact with one of said first and second quantitiesof said adsorbing agent in accordance with which of said quantities isat said'effectively constant relatively low temperature whereby saidcontacted adsorbing agent is efi'ective to retain tightly impurities ofsaid feed helium while gas of said feed helium passing through saidcontacted adsorbing agent is thereby produced as purified helium output,further supplying in each of said succeeding intervals a part of saidpurified helium output product for flowing contact with one of saidfirst and second quantities of said adsorbing agent in accordance withwhich of the said quantities is at a temperature within said range oftemperatures whereby in a first portion of said interval of time saidhelium product part contactssaid adsorbing agent at a relatively hightemperature and purges said adsorbing agent so as to reactivate saidadsorbing agent, and in a second portion of said interval of time saidhelium product part contacts said adsorbing agent attemperatureszincluding saidvrelatively low temperature of said range oftemperatures and develops a pressure upon said adsorbing agent inpreparation for utilization thereof in said immediately followingsucceeding interval, and still further supplying the remainder ofsaid'helium product as a continuous stream thereof constituted byalternate outputs flowing from said contact with said first and secondquantities of adsorbing agent. ,2. The helium purification method ofclaim 1 wherein said feed helium comprises neon as acomvponent of saidimpurities therein, and said intervals of time for said first and secondquantities of adsorbing agent are determined so as to initiate in eachinstance said time interval for reactivation of an adsorbing agentquantity before a first component impurity of neon equal duration whichis set to obtainreactivation following a production of purified heliumbefore a first component impurity of neon elutes, and wherein saidrelatively high temperature is maintained in the respec tive quantitiesfor a relatively short period of time during said intervals of time andsaid purging of saidadsorbing agent occurs contemporaneously with saidshort time period during said intervals of time.

4. The helium purification method of claim 1 wherein said relatively lowtemperature is that of-liquid nitrogen, and said relatively hightemperature is approximately 0 C.

5. The helium purification method of claim 1 wherein said feedhelium issupplied at approximately 100 cm per minute, and at a pressure of 150psig.

6. The helium'purifying method of claim 1 wherein two .consecutive ofsaid-intervals of time constitute a cycle of operation, during each saidcycle said first and second quantities of .adsorbing agent aresequentially .and second insulatorreceptacles open at the lower endsthereof and wherein said canisters are separately suspended inrespective ones of said receptacles out-ofcontactwith surfaces ofsaidreceptacles, a plurality of means supporting by suspendingconnections therefrom saidreceptacles and canisters, means supportingsaid plurality of means and accommodating therein said suspension ofreceptacles and canisters,

said accommodating means having liquid nitrogen therein at a leveleffectively covering said receptacle :means, each said suspension havingoperatively associated therewitha plurality of conduit systems adpatedto .complete gas flow passages communicating a helium gas inlet deviceto an upper section of said canister, a helium gas outlet device to saidupper section of said canister, and a nitrogen gas outlet device to aspace between said receptacle-and saidcanister, said conduit systemsfurther operatively associating with each said canister forcommunication of .a lower part.

therein .with aproduct outletconduit arrangementand a lower part in saidother canister, and program control means connected to cause operationof said .conduit system devices and heaters in said canister in apredetermined sequence wherebysaid adsorbent materials of said first andsecond canisters are separately, and inan alternate and uncomformablemanner, active to enable purification of helium and subject toregeneration, respectively, while ultrapure helium is continuouslyproduced as output from said product outlet conduit arrangement.

'8. Helium'purifying apparatus of claim 7 wherein said devices comprisesolenoid actuated valves in said flow passages, said heaters compriseelectrical resistance wires, .andsaid program control means comprisesaset of elecu'ical switches separately connected 9. Helium purifyingapparatus of claim 7 wherein 7 said nitrogen gas outlet device of eachsaid canisters responds to said program control means by closing toprevent discharge of nitrogen gas therethrough when said heater of saidcanister functions to enable regeneration of said adsorbent materialtherein,

'whereby -nitrogen gas accumulating in said space forced out from saidspace is replaced by nitrogen gas which constitutes an insulator shieldaround said canister during regeneration of said adsorbent materialtherein.

10. In a gas processing apparatus comprising a container storing liquidrefrigerant up to a predetermined level therein, a cover attached tosaid container having secured therein means supporting enclosure vesselsso as to depend from said cover into said liquid refrigerant, saidvessels being packed with adsorbent material, means controlling the flowof feed gas through said vessels for processing therein and an output ofprocessed gas from said vessels, and further means controlling adischarge from said container of gas arising from said liquidrefrigerant, means maintaining said predetermined level of liquidrefrigerant in said container including a liquid level sensor controlfor a switch actuator, said sensor control comprising a liquid levelsensing end normally submerged in said liquid refrigerant, anintermediate part extending through said cover, and a pressureresponsive flexible opposite end adapted to close a normally openelectrical switch in response to heat applied to said sensor, a sourceof liquid refrigerant and conduit means connected thereto which passesthrough said cover and situates an outlet opening thereof adjacent saidliquid level in said container, valve means determining the liquid flowin said conduit means comprising a normally deenergized solenoid, anenergizing circuit for said solenoid completed by closure of saidswitch, a length of heat conductive material having one end affixed tosaid sensing end and held to said intermediate part so as to extend to aregion in said container adjacent said cover, whereby a decrease in saidliquid refrigerant level at said sensing end permits a rapid warmingthereof by heat carried through said conductive material which producesa pressure increase closing said switch to energize said solenoid andopening said valve with the result that liquid refrigerant beingsupplied to the container raises the level of liquid therein to againsubmerge said sensing end of said sensor and return said switch andsolenoid to normal.

2. The helium purification method of claim 1 wherein said feed heliumcomprises neon as a component of said impurities therein, and saidintervals of time for said first and second quantities of adsorbingagent are determined so as to initiate in each instance said timeinterval for reactivation of an adsorbing agent quantity before a firstcomponent impurity of neon elutes during said interval of time in whichsaid quantity is contacted with said feed helium to produce purifiedhelium output.
 3. The helium purification method of claim 1, having neonas a component of said impurities, and said first and second intervalsof time thereof substantially of equal duration which is set to obtainreactivation following a production of purified helium before a firstcomponent impurity of neon elutes, and wherein said relatively hightemperature is maintained in the respective quantities for a relativelyshort period of time during said intervals of time and said purging ofsaid adsorbing agent occurs contemporaneously with said short timeperiod during said intervals of time.
 4. The helium purification methodof claim 1 wherein said relatively low temperature is that of liquidnitrogen, and said relatively high temperature is approximately 0* C. 5.The helium purification method of claim 1 wherein said feed helium issupplied at approximately 100 cm3 per minute, and at a pressure of 150psig.
 6. The helium purifying method of claim 1 wherein two consecutiveof said intervals of time constitute a cycle of operation, during eachsaid cycle said first and second quantities of adsorbing agent aresequentially effective to produce purified helium, and concurrentlytherewith said second and first quantities of adsorbing agent aresequentially purged.
 7. Apparatus for purifying helium comprising firstand second canisters, each packed with an adsorbent material andequipped with an internal heater operable to enable regeneration of saidadsorbent material, first and second insulator receptacles open at thelower ends thereof and wherein said canisters are separately suspendedin respective ones of said receptacles out-of-contact with surfaces ofsaid receptacles, a plurality of means supporting by suspendingconnections therefrom said receptacles and canisters, means supportingsaid plurality of means and accommodating therein said suspension ofreceptacles and canisters, said accommodating means having liquidnitrogen therein at a level effectively covering said receptacle means,each said suspension having operatively associated therewith a pluralityof conduit systems adpated to complete gas flow passages communicating ahelium gas inlet device to an upper section of said canister, a heliumgas outlet device to said upper section of said canister, and a nitrogengas outlet device to a space between said receptacle and said canister,said conduit systems further operatively associating with each saidcanister for communication of a lower part therein with a product outletconduit arrangement and a lower part in said other canister, and programcontrol means connected to cause operation of said conduit systemdevices and heaters in said canister in a predetermined sequence wherebysaid adsorbent materials of said first and second canisters areseparately, and in an alternate and uncomformable manner, actIve toenable purification of helium and subject to regeneration, respectively,while ultrapure helium is continuously produced as output from saidproduct outlet conduit arrangement.
 8. Helium purifying apparatus ofclaim 7 wherein said devices comprise solenoid actuated valves in saidflow passages, said heaters comprise electrical resistance wires, andsaid program control means comprises a set of electrical switchesseparately connected in energizing circuits to said solenoid actuatorsand said heater wires, and timer driven cams corresponding to saidswitches and adapted by their positional presetting with respect to saidswitches to effect a predetermined sequential operation of said valvesand said heaters.
 9. Helium purifying apparatus of claim 7 wherein saidnitrogen gas outlet device of each said canisters responds to saidprogram control means by closing to prevent discharge of nitrogen gastherethrough when said heater of said canister functions to enableregeneration of said adsorbent material therein, whereby nitrogen gasaccumulating in said space between said canister and said receptaclecorresponding thereto is pressurized to where liquid nitrogen forced outfrom said space is replaced by nitrogen gas which constitutes aninsulator shield around said canister during regeneration of saidadsorbent material therein.
 10. In a gas processing apparatus comprisinga container storing liquid refrigerant up to a predetermined leveltherein, a cover attached to said container having secured therein meanssupporting enclosure vessels so as to depend from said cover into saidliquid refrigerant, said vessels being packed with adsorbent material,means controlling the flow of feed gas through said vessels forprocessing therein and an output of processed gas from said vessels, andfurther means controlling a discharge from said container of gas arisingfrom said liquid refrigerant, means maintaining said predetermined levelof liquid refrigerant in said container including a liquid level sensorcontrol for a switch actuator, said sensor control comprising a liquidlevel sensing end normally submerged in said liquid refrigerant, anintermediate part extending through said cover, and a pressureresponsive flexible opposite end adapted to close a normally openelectrical switch in response to heat applied to said sensor, a sourceof liquid refrigerant and conduit means connected thereto which passesthrough said cover and situates an outlet opening thereof adjacent saidliquid level in said container, valve means determining the liquid flowin said conduit means comprising a normally deenergized solenoid, anenergizing circuit for said solenoid completed by closure of saidswitch, a length of heat conductive material having one end affixed tosaid sensing end and held to said intermediate part so as to extend to aregion in said container adjacent said cover, whereby a decrease in saidliquid refrigerant level at said sensing end permits a rapid warmingthereof by heat carried through said conductive material which producesa pressure increase closing said switch to energize said solenoid andopening said valve with the result that liquid refrigerant beingsupplied to the container raises the level of liquid therein to againsubmerge said sensing end of said sensor and return said switch andsolenoid to normal.